Post-delisting Monitoring Plan for the Bald Eagle - March 2009 Final

Summary

The Post-delisting Monitoring Plan (Plan) will monitor the status of the bald eagle by
collecting data on occupied nests over a 20-year period with sampling events held once
every 5 years starting in early 2009. The Plan will continue the nest check monitoring
activities conducted by the States over the past years and add census of area sample plots.
The area sample plots will be selected from eagle habitat across the contiguous 48 States
based on known nesting density. The set of known occupied nests (list frame) will be
combined with the numbers of newly identified occupied nests from the area plot samples
(area frame) to provide a dual frame estimate (Appendix 1). Statistically combining the
results of these two data sets will provide a single estimate for the bald eagle population
of the contiguous 48 States that more closely represents the actual nesting population of
bald eagles than either the traditional nest check for occupancy or area plot sampling
alone, based on our pilot studies in Maine, Minnesota, Florida, Washington and Missouri
(Appendix 1). Reduction in future nest check monitoring (list frame) by the States will
be compensated by sampling the list frame during the area plot surveys. In addition, dual
observer sampling protocols are recommended to reduce bias (Appendix 2). Some
States, particularly those with sparse numbers of nesting pairs, are currently collecting
data in a highly accurate manner and may not need to employ the dual frame
methodology. Data from these States will be included as a complete census.

The Plan recommends that the State agencies continue the occupied nest survey data
collection and submission and assist with the area surveys while the U.S. Fish and
Wildlife Service (Service) coordinates the area survey, manages the database, provides
expertise including dual frame sampling design and data analysis, and initially funds the
area sampling. This Plan is not intended to replace specific plans to manage eagles or
monitor them in a different manner for specific management purposes.

The sample design is based on an 80 percent chance of detecting a 25 percent or greater
change in occupied bald eagle nests over any period, measured at five-year intervals. We
believe this is a goal that will both ensure recovery and be cost-effective. Were this
degree of decline to occur with no further increase, the bald eagle population would still
be at a level recognized as recovered (from 9,789 occupied nests when the bald eagle was
delisted in 2007 to 7,342 occupied nests, a 25 percent reduction) based on a population
estimate of 6,471 when the initial proposal to delist was published in 2000. If such
declines are detected, the Service’s Bald Eagle Monitoring Team in conjunction with the
States will investigate causes of these declines, including consideration of natural
population cycles, weather, productivity, contaminants, other mortality factors, habitat
changes or any other significant evidence. The result of the investigation will be to
determine if the population of bald eagles in the contiguous 48 States warrants expanded
monitoring, additional research, and/or resumption of Federal protection under the
Endangered Species Act (ESA). At the end of the 20 year monitoring program, we will
conduct a final review. It is the intention of the Service to work with all our partners
toward maintaining continued species population expansion and management.